Process of producing calcium cyanamid.



I. H. LlDl'lOLh/l. PROCESS 0F PRODUCING CALCIUM CYNAMID. `Awucfmon man rss. 14, 1914.

'Patented May 23, 1916.

` 1o l t `lllrereuctionbetweencalcium carbid and To all whom trudy/iconcern: 1 Vlie 1t` knownfthat 1,', JOHAN y y UNITED sTATEs PATENT omen.

i :ionen nihtrmn LIJJHOLM,` or Lennon, nNeLANn.

'. :enocnss orprnonucine cALcIUM cYANAMIn.

Specification of Letters Patent.

Patented May 23, i916.

Application mea February 14,1314.' seriaino. 518,789.

l den, residingat London, Greatfritain,have

'invented new and 'usefulImprovements Processesof Producing Calcium Cyanamid,

of whiclithe following is a specification.

` "llhi'sinvention relates to an improved 1,

`precess of' producingwc'a'lciuln 'cyanarnid fronigcalciuin ,carbid und nitrogen.

- nitrogen`is performed according to fthe fermait-f .icacspriy-:oaugfoiiiy i Said reaction is, asis well known, exother- Inic ,andbegins at atexnperature of 'about ciuin cyanainid'jmust bein a finely dividedV porous stateso that Athe nitrogen has accessil to every Vparticle ofthe calcium carbid, A

V:z5 i cyananiidxis easilyI sintered, the sintering A 1,000to1100" C., if no special 4arrangendenis a'renia de 4for lowering `the reaction telnperature. Forgperforrning the reaction, the calspeciaivdiiiiculty in performing said teau# tion' isca'used by the fact'that the `c aylciurn talringfplace .at ,a temperature whichV lies y only la few hundred degrees ,centigrade' above thehusual ireaction temperature and causesraniirnrnediate interruption ofthe re-A actioninthatthe sintered massprevents the accessofjti-i'e :nitrogen to ,the carbid which has not been converted into calcium cyanalnidg,Z L,Such anelevation" of the temperature to and above the sintering temperature readilytalies place on account of the heat developed jbythereactiom especially if the spejedoi` the reaction is too great.y Generally thei,reactiontemperature is,l therefore, lowered `by an addition of catalytic substances, such yascalcium` chlorid orcalcium fluorid, whereby therange between the starting ternperatureftor thereaction and the sintering temperature isincreased,L andan elevating of the teuiperatureto theisintering temperature is more easily avoided. Under such circumstances the reaction, however, `requires a long time, for instance'() hours for a charge of 500 kgs., and the yield x'will always rest considerably under itsl theoretical value. `It

has hitherto,beenythought that Athe losses were caused due ,to the cyanarnid reaction being"afreversibleprocesshaving its reversing'pointat about 1360" C., andthat accordingly, themcst favorable condition in but to av smaller extent than the reaction f formula (1) and accordingly it is possible by using a suflicient high temperature of reaction to obtain a practically theoretical yieldifofA 'calcium cyanamid. At a tempera-V ture of 1500"` C., the speed of reaction is highly increased and i.ncreases.further accordingto the rise in temperature, so that it is practically instantaneous and of an eX- plosive nature 'a temperature of 2000o C. Because the temperature used according to this invention exceeds the melting point 0f the calcium cyaamid, care is t0 be taken "that said incitingy doesy not form any hindrance to the performing of the reaction. This is eiected by spreading the carbid in the form of a powder into the nitrogen during the reaction, so that the'freaction-is per formed in eachy separate particle of carbid, ere it comes into contact with other particles of carbid. The particles are, preferably,

cooled after performing the reaction, while being, still spread in the nitrogen whereby,

after the particles have passed through' the nitrogen and been acted upon by the reaction, their conglolneration is obviated. The necessary heating may be .eiected by heating the carbid and the nitrogen sepa- .rately or both simultaneously. Thus for instance the nitrogen may be `heated lelec-- trically to the necessary temperature, for instance-2000o C., and the powdered carbid may be .caused to fall down through this gas, or thepowdered carbidrnay be'brought to fall through a furnace chamber-containing nitrogen, the walls of which are heated electrically to such a hightemperature that they heat, by radiating, 'the falling powder of carbid to a corresponding temperature, thereby causing it. to react instantaneously with the nitrogen. The dissociation of the calcium. cyanainid formed is then prevented i by eeeiing aie felling powder immediately after the performance of the reaction to a temperature below the temperature of dis- .Referring to the drawing, the furnace4 consists of a tube l made of a suitable refractory land electrically conducting material as for instance carbon,` and forming the chamber of reaction proper. To the said tube electric currentmay be supplied by the contact blocks 2, 3 attached to the ends of .the tube and, preferably, provided with At the top' wateror air-cooling devices. the tube is provided with a feeding hopper 4 which at the bottom has a sieve 5l through 'which the linely ground carbid introduced through i the hopper may be sifted down through the tube l. Below the chamber of reaction is located a cooling zone or cooling v-cl'iamber 6, provided, ]neferably,`.withI hollow walls ofiinetal filled with 'atei'. At the bottom of the cooling chamber there is prof vided a feeding screw 7 of anyother suitable device for removing` the finished material from the furnace. The vertical, electrically conducting tube l is surrounded by a mantle 8 at the upper part of which. isl arranged an inlet 9 admitting the nitrogen.

The block 3 formed with a channel 10 admitting the nitrogen into the furnace. The nitrogen thus passes the space between vthe mantle 9 and the tube l and, consequently,- enters'the furnace strongly preheated. said space is, preferably, filled up with pier-es of charcoal in' order to facilitate the lpreh'e; ig of the nitrogen and at the saine tinieto-consume the oxygen which possibly might accompany the nitrogen. Around the mantle placed a suitable heat non-conducting iiiaterial, not shown inthe drawing. #After the apparatus has been' filled with nitrogen,` an electric4 current is conducted throi'igh the tube 1 which thereby is heated to the temperature desired, for instance '20000 `(l.'" -Then the feeding of carbid into the furnace commences. The nely divided "powder of carbidfalling down through the sieve is heated during its passage through 'the furnace by the heat rai'liating from the `tu'lj e l and is rapidly brought to a tempera- 'tfre farexcceding the temperature of reaction. Owing'torthis, a sudden explosion-like combl-istion ofthe' powder of carbid .takes place in the nitrogen in about the same inanner as'wlien. .coal-powder is caused to fall down through strongly heated air. vThe heat developed during the reaction contributes in a high degree to the-maintaining o'ff The 'the temperature lof the furnace, and, on account thereof, thefstrength of the current Iflowing through the. tube 1 may be reduced considerably when the process has started. The powder of cyanamid falling through the lower part of the furnace gives olif a great part of its heat to the cooled wall of this 4part of the furnace so that it is compaz tively cooled when reaching the bottom of the furnace. The material collected on the bottom of the furnace willr be still more cooled, because of the bottom being wateri cooled. Sintering or conglomerating of the material will thereby be obviated, and the .feeding screw will deliver the calcium cyananiid in the forin of powder or grains. The sudden cooling of the calcium lcyanamid immediately after the formingthereof prelvents losses of nitrogen on account of dissociation, and owing thereto one will, b

sizing suitably the furnace and using a su ficiently high temperature, be able lto obtain, from practical point of view, a theo-y retical output of calcium cyanamid.

It will be easily understood that the furnace described above is only one of the plurality of constructions which may be used in the practical perforn'iing of the process. Thus for instance, the material. need not necessarily be heated by means -of the heat generated in a resistance, since' the tube 1 may be replaced by a tube or alchaniber of 'reaction in which one or more horizontal or vertical electric arcs aiestruck and effect the heating. Said arcs may also, in' Well known inannerbe extended `,in the vshape .of disks. instead of having`tlie. powder. of carbid fall down yby its ownweight, it may be blown upwardthrough the tube or the heating chamber /o/r spread horizontally by means of a. centrifugal disk through a furnace of reaction heated to a high temperaturel f )f course, the process may be performed by subjecting .the nitrogen to overpressure as well as with or without additions of known kind to the carbid without deviating Icalcium carbid into the nitrogen'in a cham- ,ber of reaction, and heating.,T the walls of said chamber to heat the calcium carbid to a temperature above the melting point of calcium cyinemld.

3i The processo'f producing` calcium cyan-` lai-mid `from calcium carbid 'and nitrogen,

which `comprises spreading finely -divided calcium carbid into the nitrogenin e cliz1=mberofreection, heating the Walls of said i chamber to heat the calcium carbid und the nitrogen to a. temperature above the melting point of czilclum cynnanud, 'and cooling the I 4;' The process of producing calcium cyan- "amid from calcium carbid and nitrogen,

which comprises 4spreeoling finely divided x calcium carbid into the nitrogen in a chainbei` of reaction, the Walls of which are ele@ trically heated to such e temperature that they are capable of heating the calcium carbid und the nitrogen to n temperature above the melting point of calcium cya-namid, thus performing the reaction While the carbid is suspended in the nitrogen, and conducting the calcium cyanamicl through a, cooling zone. y

In testimony that I claim the foregoing as my invention, I have signed my name in presence of two subscribing Witnesses.

JOHAN HJ ALMAR LIDHOLM. `Witnesses J. CALLEsoN HOILEY,

MURRAY A. CARSER. 

